Im using MTL in my tiburon back when they specced 75w90 and it has worked great.I`ve used Redline MTL on my last 3 cars, i love that oil. It made gearchanges noticeable better.
Worked out fine? Did you UOA the fluid for comparison? disassemble the transmission to study the wear patterns, as compared to an identical transmission that didn't get the synchromesh? Or run either and compare the magnetic drainplugs to see if a thick or thin fluid were 'similar?
Light loads, no power mods, low operating temps, or maybe a stronger than needed manual... survived a thinner fluid.
Only good thing is that the Valvoline, and not the Pennzoil, claims 'GL4'. So, either Valvoline shook the salt/pepper shaker of additives a little more, or played around with the base oils and viscosity modifier in the formula for 'better protection'.
Recommendations here are hit or miss, and sometimes foolish. I would not use a 9cst fluid if my transmission was R&D'd for a 12 or 14cst fluid without understanding the 'possible' consequences.
Does picture below say to be used in place of 75w85 or 75w90?